The mechanisms of the general acyl CoA dehydrogenase is under investigation. Approaches include rapid kinetics, the use of pseudosubstrates and "suicide substrates", chemical modification of the dehydrogenase and the electron transfer flavoprotein (ETF) and electrochemical analysis of the dehydrogenase and ETF flavins. It is proposed to identify the amino acid residue in the dehydrogenase that is modified by the suicide substrate, 3,4-octynoyl CoA. Preliminary experiments indicate that the residue is a methionine. Experiments are also planned to investigate the kinetic significance of a flavin semiquinone observed on mixing the dehydrogenase with octanoyl CoA. Studies are also proposed using substituted derivatives of the pseudosubstrate, furyl propionyl CoA which upon oxidation yields a chromophoric enoyl CoA. The planned experiments involve an investigation of substituent effects with acyl CoA derivatives substituted on the furan ring. Finally the potentials of the ETF flavin will be determined having designed a satisfactory analytical system.